Method for making a foundation pile

ABSTRACT

The invention relates to a method for arranging a foundation pile in the ground using a ground displacement drill, wherein a hollow drill pipe with a ground displacement drill attached thereto are jointly introduced as a foundation pile, with the aid of a pile cap coupled to the hollow drill pipe, into the ground under axial pressure, whilst rotating, and wherein during the introduction into the ground, via a liquid supply extending through the pile cap and the foundation pile, a liquid medium is supplied through the ground displacement drill to the ground, and wherein, after the foundation pile has been arranged sufficiently deep in the ground, the pile cap is thereupon uncoupled from the foundation pile and retracted from the ground, leaving the foundation pile behind, wherein during retraction of the pile cap, liquid is supplied via the pile cap to the space formed between the pile cap and the foundation pile. Further, the invention relates to a pile cap and a foundation pile which are used in the method according to the invention.

This invention relates to a method for arranging a foundation pile inthe ground, wherein a hollow drill pipe with a ground displacement drillattached thereto are jointly introduced as a foundation pile, with theaid of a pile cap coupled to the hollow drill pipe, into the groundunder axial pressure, whilst rotating, and wherein during theintroduction into the ground, via a liquid supply extending through thepile cap and the foundation pile, a liquid medium is supplied throughthe ground displacement drill to the ground, and wherein, after thefoundation pile has been arranged sufficiently deep in the ground, thepile cap is thereupon uncoupled from the foundation pile and retractedfrom the ground, leaving the foundation pile behind.

The invention further relates to a foundation pile.

The method referred to is based on the method according to NL 189365 andis known from practice. The method is typically employed in situationswhere pile driving is not possible, for instance because this entailstoo much nuisance. In such situations, a foundation pile is coupled to apile cap and subsequently introduced into the ground under axialpressure whilst rotating. During the introduction of the foundation pileinto the ground, via a liquid supply extending through the pile cap andfoundation pile, a liquid medium is supplied through the grounddisplacement drill to the ground. In particular, a cement emulsion canbe supplied to the ground through the tip of the ground displacementdrill as soon as a supporting layer is reached. What is achieved bysupplying the liquid medium referred to is that the rotation resistanceof the foundation pile with respect to the ground is reduced. What canbe further achieved by supplying the cement emulsion referred to intothe supporting layer is that the foundation pile is eventually fixedunder the ground level with additional firmness. After the foundationpile has been arranged sufficiently deep in the ground under groundlevel, the pile cap can subsequently be uncoupled from the foundationpile, and, whilst leaving the foundation pile behind, be pulled backthrough the top layer of ground situated above the supporting layer.According to this method, the upper ends of the foundation piles arearranged in the ground far below ground level, whereafter a top layer ofground situated above the supporting layer is subsequently removed forrealizing a building pit or tunnel entrance. Often, the building pit ortunnel entrance is flooded after being excavated. In such a case, forinstance an underwater concrete floor is poured, with the concrete floorbeing anchored to the foundation piles. After curing of the concretefloor, the building pit or tunnel entrance can be pumped dry. Dependingon the specific construction of the building pit or tunnel entrance, thefoundation piles thereupon take up a tensile load exerted by the waterpressure on the underwater concrete floor. Naturally, if the buildingpit or entrance can remain dry, a concrete floor can be poured directlyafter excavation.

A disadvantage of the method mentioned is that as a result of theretraction of the pile cap from the ground, liquid flows are created inthe ground in or near the foundation pile, so that disturbances in thesoil structure adjacent the foundation pile may arise. In particular,there may arise disturbances in the mixing ratio of the cement emulsionreferred to, so that the quality of the mixture diminishes. As a result,the bearing capacity of the foundation pile may be adversely affected.Further, the bearing capacity of the foundation layer itself may beaffected. Furthermore, an undesirable liquid flow may be created via theground displacement head through the supply line to the upper side ofthe foundation pile. This entails the possibility of the liquid flowscarrying soil particles through the ground displacement head into thefoundation pile.

The object of the invention is to provide a method of the type mentionedin the opening paragraph hereof, by which the disadvantages mentionedare prevented whilst maintaining the advantages thereof.

To that end, the method according to the invention is characterized inthat during retraction of the pile cap, liquid is supplied via the pilecap to the space formed between the pile cap and the foundation pile.This prevents a reduced pressure arising between pile cap and foundationpile, so that undesirable liquid transport resulting from pressuredifferences is prevented.

In a further embodiment of the method according to the invention, duringuncoupling, the liquid supply is divided into a first part extendingthrough the pile cap and a second part extending through the foundationpile, and during retraction, liquid is supplied via the first part tothe space formed between the pile cap and the foundation pile. In thismethod, during uncoupling of the foundation pile and the pile cap, theliquid supply is split into a first and a second part. As a consequence,it is possible during drilling to use the first part and the second partof the liquid supply for supplying the liquid medium to the ground, andduring retraction to use the first part of the liquid supply forsupplying the liquid medium to the space between the pile cap and thefoundation pile for preventing the pressure differences mentioned duringretraction of the pile cap.

In a further elaborated method according to the invention, aftersplitting of the liquid supply, the second part of the liquid supply,extending through the foundation pile, is closed off. This can beachieved, for instance, by including a non-return valve in the secondpart of the liquid supply. What can thus be prevented is the onset of aliquid flow from the drill tip via the second part of the supply line.What can further be achieved is that in a situation where duringdrilling the supply of the liquid medium through the liquid supplyfalters, soil particles are prevented from ending up via the grounddisplacement drill in the second part of the liquid supply. It is notedthat such a ground displacement drill provided with a non-return valvemay in itself already be used advantageously in drilling without a pilecap.

The invention further relates to a foundation pile for fixingengineering structures below ground level, comprising a hollow drillpipe carrying a ground displacement drill at a first end, whichfoundation pile is provided with a supply line extending from a secondend of the drill pipe through the drill pipe and terminating at theouter surface of the ground displacement drill, which supply line isprovided with a coupling piece adjacent the second end of the drillpipe.

Such a foundation pile is known from U.S. Pat. No. 3,842,608. U.S. Pat.No. 3,842,608 describes a foundation pile comprising a hollow pipe,having a ground displacement drill attached at one end. Through the pipeextends a liquid supply terminating in openings in the grounddisplacement drill.

This foundation pile is filled with cement and provided with a helicalprofile at its outer side. Provided between the windings of the profileare further openings in which the liquid supply terminates.

A drawback of the foundation pile according to U.S. Pat. No. 3,842,608is that liquid may undesirably flow in from the drill tip via the supplyline.

U.S. Pat. No. 3,636,718 describes a similar cement-filled foundationpile which is open at the top. With this foundation pile too, anundesirable liquid flow from the drill tip to the supply line can occur.

EP 0 228 138 describes a reusable, hollow drill pipe, through whichduring retraction cement can be injected into the drilled hole. Toprevent an undesirable liquid flow, the hollow drill pipe may beprovided at its underside with a non-return valve or with a drill headwhich functions as lid during drilling and upon retraction is leftbehind in the ground.

To prevent, during retraction of the pile cap, an undesirable liquidflow from the drill head through the supply line to the interspaceformed, the foundation pile according to the invention is characterizedin that the supply line is provided with a non-return valve.

Preferably, the non-return valve is arranged in or adjacent the grounddisplacement drill. In a situation where during drilling the pressureoutside the ground displacement drill is higher than the pressure in thesupply line, the non-return valve will close. As a result, soilparticles can be prevented from penetrating into the supply line of thefoundation pile.

The foundation pile can be coupled to a pile cap with the aid of thecoupling piece. With the aid of the pile cap, a couple can subsequentlybe exerted on the foundation pile for drilling the foundation pile intothe ground. The coupling piece is arranged such that the pile cap canexert a couple via the coupling piece on the foundation pile and that aliquid supply situated in the pile cap can be coupled substantiallyleakage-free to the supply line extending through the foundation pile.

In a further embodiment of the foundation pile according to theinvention, the drill pipe is provided at a second end with a closingplate, and the coupling piece is designed as a length of pipe extendingin axial direction of the drill pipe beyond the closing plate. Theclosing plate serves to prevent dirt and soil penetrating into thefoundation pile after the foundation pile has been uncoupled from thepile cap in the soil under ground level. After the concrete floor hasbeen poured in the building pit, and after the building pit, ifrequired, has been rendered dry, the closing plate can be cut off fromthe foundation pile. Thereupon it is possible to fill up the foundationpile with, for instance, concrete and reinforcement steel. What is thusachieved is that the foundation pile does not need to be filled withcement during drilling.

The invention further relates to a pile cap and to a ground displacementdrill for a foundation pile.

Further advantageous embodiments of the invention are described in thesubclaims.

The invention will presently be further elucidated on the basis of anexemplary embodiment represented in a drawing. In the drawing:

FIG. 1 schematically shows a vertical cross section of a pile capaccording to the invention and a foundation pile according to theinvention arranged below ground level in a supporting layer situatedbelow a top layer;

FIG. 2 schematically shows a vertical cross section of a foundation pileaccording to the invention arranged below ground level and anchored toan underwater concrete floor poured in a building pit;

FIG. 3 schematically shows in detail a longitudinal section of a secondend of a foundation pile according to the invention;

FIG. 4 schematically shows a longitudinal section of a lower end of apile cap according to the invention;

FIG. 5 schematically shows a longitudinal section of a pile capaccording to the invention which is coupled to a foundation pileaccording to the invention;

FIG. 6 schematically shows a perspective view of a ground displacementdrill according to the invention.

It is noted that the Figures are only examples of a preferred embodimentof the invention. In the Figures, identical or corresponding parts areindicated by the same reference numerals.

With the aid of the method according to the invention, foundation pilescan be installed far below ground level for the purpose of fixingengineering structures. The piles can be used, for instance, foranchoring, through their upper ends, constructions on the bottom ofbuilding pits, such as a concrete floor for a tunnel entrance, which ispoured under water in a building pit which has been excavated afterinstalling the foundation piles.

In FIG. 1 the method according to the invention is further illustrated.In this Figure, a foundation pile 2 has been installed in the groundbelow ground level. The foundation pile 2 comprises a hollow drill pipe6 to which the ground displacement drill 4 is attached. The hollow drillpipe 6 was detachably coupled to a pipe sleeve 8 of a pile cap 10 (seeFIG. 5) for introducing the foundation pile 2 into the ground underaxial pressure, whilst rotating. The cap 10 thereby exerted a torque onthe foundation pile 2, so that the foundation pile 2 was rotated aboutits longitudinal axis, with the ground displacement drill 4 penetratingthrough a top layer B of the ground into a supporting layer S of theground, situated below the top layer B. During drilling, via a liquidsupply 12.1, 12.2 extending through the pile cap 10 and the foundationpile 2, a liquid medium was supplied through the ground displacementdrill 4 to the ground. The liquid medium flowed through an opening 14 ofthe ground displacement drill 4. After the foundation pile 2 had beenarranged sufficiently deep in the ground, the pile cap 10 wassubsequently uncoupled from the foundation pile 2, whereupon the pilecap 10 could be retracted from the ground, leaving the foundation pile 2behind in the ground. This is the situation achieved in FIG. 1.

During retraction of the pipe sleeve 8 of the pile cap 10, asrepresented in FIG. 1, a liquid medium is supplied via a first part 12.1of the liquid supply 12.1, 12.2, to the space 16 formed between the pilecap 10 and the foundation pile 2, surrounded by the top layer B of theground. This prevents significant pressure differences arising in theground as a result of the retraction of the pile cap 10. What is thusachieved, for one thing, is that as few liquid flows as possible arisealong or through the foundation pile 2, and what is further achieved isthat the foundation pile 2 during retraction of the pile cap 10 is notsucked away from its position.

The foundation pile 2 includes a second part 12.2 of the liquid supply12.1, 12.2. The second part 12.2 of the liquid supply can be closed offby a non-return valve 18 included in the second part 12.2. Thisnon-return valve 18 in this example is included near the opening 14 ofthe foundation pile. In a situation where the foundation pile 2 iscoupled to the pile cap 10 for drilling with the ground displacementdrill 4, it may happen that the supply of a liquid medium via the liquidsupply 12.1, 12.2 falters temporarily. As a consequence, the pressure inthe second part 12.2 may be temporarily lower than the pressure in thesoil adjacent the ground displacement drill 4. In this case, thenon-return valve 18 closes, so that no liquid flows with soil particlescan penetrate into the second part 12.2.

The liquid supply 12.1, 12.2 is sometimes referred to as grout line.During drilling, via the grout line, as indicated above, a liquid mediumcan be supplied to the soil via the opening 14. However, it is equallypossible via the grout line to supply a cement emulsion 20 to the soilas soon as a sand layer is reached during drilling. With the cementemulsion 20, the foundation pile 2 can be fixed in the ground extrafirmly.

FIG. 2 shows a foundation pile 2 arranged in the supporting layer S ofthe ground after the top layer of the ground B has been removed forforming a building pit and after an underwater concrete floor has beenpoured. The foundation pile 2 is anchored to a underwater concrete floor22. For anchoring the concrete floor 22 with the foundation pile 2, thefoundation pile 2 is provided with two flanges or rings 24.1 and 24.2.The cement emulsion 20 injected into the supporting layer S is clear tosee in the Figure. This cement emulsion 20 is sometimes referred to asinjected soil or mixed-in-place blend. In the Figure it is further shownthat the second part 12.2 of the supply line 12.1, 12.2 projects by acertain length above the hollow drill pipe.

In FIG. 3, the second end of the drill pipe 6 is represented in moredetail. The drill pipe 6 is provided at the upper end with a couplingpiece 26. Adjacent the second end, the drill pipe 6 is further providedwith a closing plate 28. The closing plate 28 serves to prevent dirt andsoil penetrating into the foundation pile 2 when the foundation pile hasbeen installed in the ground and the pile cap has been or is beingretracted. The closing plate 28 extends substantially transversely withrespect to the longitudinal axis of the foundation pile 2, engaging aninner wall of the foundation pile as well as the second part 12.2 of thesupply line 12.1, 12.2. The closing plate 28 can be removed after curingof the concrete floor 22 and after the building pit has been pumped dry,so that the foundation pile 2 can be filled up with cement. In theexample of FIG. 3, the coupling piece 26 is designed as a length of pipereaching beyond the closing plate 28 in axial direction of the drillpipe 6.

The foundation pile 2 in FIG. 3 is provided with a moment absorbingplate 30 which is arranged between the second part 12.2 of the supplyline 12.1, 12.2 and the inner wall of the foundation pile 2. The momentabsorbing plate 30 extends substantially transversely to thelongitudinal axis of the foundation pile 2 and is mounted on the innerwall of the foundation pile 2. The moment absorbing plate 30 is providedwith a recess 32 which surrounds the second part 12.2 of the supplyline. The moment absorbing plate 30 is situated at a smaller distancefrom the second end of the drill pipe 6 than the closing plate 28.

FIG. 4 shows a lower end of the pipe sleeve 8 of the pile cap 10. InFIG. 4, an arrow indicates where the first part 12.1 of the liquidsupply 12.1, 12.2 terminates in a sleeve coupling 32. Through sliding inaxial direction, this sleeve coupling 32 can be detachably coupled tothe coupling piece 26 of the foundation pile 2. The sleeve coupling 32is thereby slipped over the length of pipe of the foundation pilereaching beyond the closing plate. The sleeve coupling 32 can comprise asealing, such as an O-ring, so that the first part 12.1 can be coupledat least substantially leakage-free to the second part 12.2 of theliquid supply. The hollow pipe sleeve 8 of the pile cap 10 furthercomprises a moment transfer projection 34 capable of cooperating withthe recess 32 of the moment absorbing plate 30 of the hollow drill pipe6 of the foundation pile 2.

In FIG. 5 it is shown that the hollow drill pipe 6 of the foundationpile 2 can be coupled to the pipe sleeve 8 of the pile cap 10. In theFigure, it can be seen that when this coupling is effected, the firstpart 12.1 of the liquid supply is coupled to the second part 12.2 of theliquid supply 12.1, 12.2. After the pile cap 10 has been coupled to thefoundation pile 2 in the manner indicated in FIG. 5, drilling can takeplace. During drilling, the pile cap 10 transmits a couple to thefoundation pile 2 via the moment absorbing projection 34 via the momentabsorbing plate 30. During drilling, via the coupled parts of the liquidsupply 12.1, 12.2, the liquid can subsequently be supplied to the groundthrough the foundation pile 2 via the ground displacement drill 4.

FIG. 6 represents a ground displacement drill 4 on a somewhat largerscale. The ground displacement drill 4 can be used as part of thefoundation pile 2 according to the invention. The ground displacementdrill 4 comprises a substantially cone-shaped drill head 54 which isprovided with one or more openings 14 for supplying a liquid medium fromthe liquid supply 12.1, 12.2 to the soil. The openings 14 are preferablyprovided near the tip 40 of the drill in the outer surface of the drilltip, so that the liquid medium is chiefly supplied to the soil near thedrill tip 40 of the ground displacement drill 4. The drill head isprovided with coupling means not represented in the figure, for couplingto the liquid supply 12.1 and 12.2. Preferably, between the couplingmeans a length of pipe or bore is included which terminates in one ormore openings 14 at the outer surface and in which a non-return valve isincluded. The drill head carries a substantially cylindrical edge 42 forcooperation with the end of the drill pipe 6.

In general, the inside diameter of the cylindrical edge 42 of the grounddisplacement drill 4 will be somewhat greater than the outside diameterof the drill pipe 6 of the foundation pile 2. Provided on the drill head54 and/or the cylindrical edge 42 are cutting and displacement members,for instance designed as spirally configured ridges 50, 52. The ridges50, 52 are provided with cutting teeth 56, which on the one handfacilitate drilling through relatively hard layers and on the other handmay be active as mixing members for the liquid medium supplied, such asgrout, cement or the like, possibly with material of the drilled layers.

During drilling, ground particles are displaced in lateral direction bythe parts 50 of the spiral ridges 50, 52. However, these particles canalso move in upward direction along the drill head 54. This is certainlythe case when the ground around the head 54 as a result of horizontaldisplacement is already so compacted that no further compaction in thehorizontal direction is possible. These ground particles moving inupward direction along the rotating ground displacement drill 4 end upfrom the outer side of the part 50 of the spiral ridges 50, 52 on theupper side of the part 52 of these spiral ridges and are then forced invertical direction by this part. The ground particles eventually end upin the place where the ground gives the least back pressure. Due to theportions 52 of the spiral ridges having a small pitch, they exert agreat displacing force on the ground particles.

The invention has been described on the basis of a few preferredembodiments. However, the invention is not in any way limited to theseembodiments. As will be clear to the skilled person, there are manyother embodiments that also fall within the scope of the invention asset forth in the following claims.

1. A method for arranging a foundation pile in the ground, wherein ahollow drill pipe with a ground displacement drill attached thereto arejointly introduced as a foundation pile, with the aid of a pile capcoupled to the hollow drill pipe, into the ground under axial pressure,whilst rotating, and wherein during the introduction into the ground,via a liquid supply line extending through the pile cap and thefoundation pile, a liquid medium is supplied through the grounddisplacement drill to the ground, and wherein, after the entirefoundation pile has been arranged sufficiently deep in the ground belowground level, the pile cap is thereupon uncoupled from the foundationpile and retracted from the ground, leaving the foundation pile behind,characterized in that during retraction of the pile cap, the liquidmedium is supplied via the pile cap to the space below ground levelformed between the pile cap and the foundation pile.
 2. A methodaccording to claim 1, wherein during uncoupling, the liquid supply lineis divided into a first part extending through the pile cap and a secondpart extending through the foundation pile, and during retraction, theliquid medium is supplied via the first part.
 3. A method according toclaim 2, wherein the second part of the liquid supply line, extendingthrough the foundation pile, is closed off.
 4. A method for arranging afoundation pile in the ground, said method comprising: coupling a pilecap to a foundation pile including a hollow drill pipe having a grounddisplacement drill attached thereto; driving said foundation pile intothe ground; supplying a liquid medium through the ground displacementdrill during the introduction of the foundation pile into the ground,via a liquid supply line extending through the pile cap and thefoundation pile; uncoupling the pile cap from the foundation pile afterthe foundation pile has been driven below ground level; and retractingthe pile cap from the ground, wherein during retraction of the pile cap,the liquid medium is supplied via the pile cap to the space below groundlevel formed between the pile cap and the foundation pile.
 5. The methodaccording to claim 4, wherein the liquid supply line is divided into afirst part extending through the pile cap and a second part extendingthrough the foundation pile, and during retraction, the liquid medium issupplied via the first part to the space below ground level formedbetween the pile cap and the foundation pile.
 6. The method according toclaim 5, wherein the second part of the liquid supply line, extendingthrough the foundation pile, is closed off.
 7. The method as in claim 4,wherein, a portion of the liquid supply line is disconnected from theground displacement drill during retraction of the pile cap.